The present invention relates to an image pick-up apparatus, and more particularly, to a camera which picks up images with a solid image pick-up element and a silver halide camera equipped with an electronic viewfinder.
An ordinary camera (hereinafter referred to as a silver halide camera) which employs a silver halide film for photographing is equipped with an optical viewfinder which is structured so that an object to be photographed can be confirmed.
The silver halide camera of this kind has had a problem that what has been photographed actually can not be confirmed immediately after photographing, which is different from a video camera and a digital camera.
(1) For the confirmation of this kind, it is considered to provide on a silver halide camera an electronic viewfinder composed of a solid image pick-up element (such as CCD and others) and a liquid crystal display device (LCD). However, some problems stated below are feared for the reason that a dynamic range of a solid image pick-up element such as CCD is narrow, compared with a latitude of a silver halide film.
-1- There happens an occasion where a range which represents an optimum exposure for a silver halide film does not represent an optimum exposure on the part of the electronic viewfinder. Namely, a small difference in an amount of light received by a solid image pick-up element is displayed on an LCD as a big difference in light intensity.
-2- For the same reason, there sometimes happens a phenomenon (a false night view) wherein a background is extremely dark on the part of an electronic viewfinder due to a difference of luminance between a primary subject and a background especially when an electronic flash is used for photographing.
-3- On the electronic viewfinder, an electronic shutter employing CCD controls exposure without being equipped with an iris aperture. It is therefore impossible to confirm a depth of field in a silver halide camera. In this case, even when an iris aperture is simply provided, a false night view tends to be caused for the same reason as that in -2- above, which is a problem.
-4- Even when an automatic electronic flash is used, it is difficult to adjust a quantity of light for both a silver halide film and a CCD at the same time. In particular, this phenomenon is remarkable when there is a big difference of sensitivity between a film and a CCD. Incidentally, when the film sensitivity differs greatly from the CCE) sensitivity, it is possible to cope with this problem by shifting an aperture on the part of the CCD from that on the part of the film. In this case, however, an aperture on the part of the CCD requires aperture mechanism which is extremely accurate.
(2) On the other hand, in view of a disadvantage caused when an automatic electronic flash is used, it is also considered to use an electronic flash of a flashmatic control type. The flashmatic control implies the control wherein an electronic flash is caused to emit light at its full power without controlling an amount of light emitted from the electronic flash, and an aperture value is determined so that the product of the distance to the subject and the aperture value is equal to the guide number of the electronic flash.
However, even under this flashmatic control, another trouble stated below is feared.
-5- Under this flashmatic control, it is necessary to control an aperture value accurately. However, on the CCD wherein a light-receiving area is smaller than that of a film, accuracy is required to be improved for the smaller light-receiving area. Accordingly, there is caused a problem that an aperture device on the part of the CCD is expensive in cost and large in size.
As stated in "-1-" to "-5-" above, it has been difficult for both cases of an automatic electronic flash and a flashmatic control electronic flash to make exposure for photographing on a silver halide film and exposure for image pick-up on a CCD to be compatible with each other.
As stated above, a CCD has a problem that accuracy of an aperture for the CCD needs to be improved, and the following problem is further caused to be related to the aforesaid problem.
-6- Though operations of an aperture are checked and adjusted in the course of its manufacture, there is caused a difference between an appropriate aperture value and an actual aperture value for light emission to make exposure to tends to be unstable, because various changes such as a change with time, a change with temperature and a change with humidity which can not be expected in manufacture are caused on the aperture afterwards. In particular, this phenomenon is more conspicuous on a CCD having the smaller light-receiving area than that on a silver halide film than on the silver halide film. To eliminate the changes mentioned above, the aperture mechanism which is of higher accuracy is needed, and higher cost and larger size of the aperture are caused. On the other hand, in a digital still camera equipped with an electronic flash, an automatic electronic flash control is employed to make an amount of exposure in photographing with an electronic flash to be an appropriate value. However, there has been a problem in the automatic electronic flash control that mechanism is complicated and a product is large in size and high in cost.